The Drake Equation – What are the Chances of Extraterrestrial Life?

At 13.2bn years, the Milky Way is almost as old as the universe itself.

​With advanced telescopes, we can now identify planets larger than Earth in other solar systems (exoplanets). 40%+ of sun-like stars have planets, but many are undetectable. So it may be closer to 100%.

Much debate surrounds this key number. Many exoplanets are outside the habitable zone for life or are too close to superhot parent stars.

​Drake assumed all Earth-like planets develop organic life. Using Earth as evidence though makes life seem inevitable. Discovering life on Mars or elsewhere would dramatically resolve this uncertainty.​

Hotly debated! Skeptics point out that from billions of species, just one has become intelligent. Others argue that life evolves towards complexity - so intelligence is inevitable.

Would alien life ever invent radio? Even an advanced civilizations might only progress to agricultural-level technology like the Roman or Chinese empires.

How long does a civilization last? Could a society overcome all threats to its survival and then endure for millions of years?

Optional addition allows for the chance of civilization to re-evolve after collapse. An intuitive addition if you consider the billion year lifespan of planets.